Stromatolite, Cyclomedusa or something else from Italy?

[adriano]

Dear all,

yesterday I went out for some hiking on Monte Faito (https://en.wikipedia.org/wiki/Monte_Faito), a Mesozoic mountain near Sorrento/Pompeii/Napoli, in the south of Italy. This 1400m mountain is mostly made of dolostone (https://en.wikipedia.org/wiki/Dolostone) and limestone - like Dolomites in the north of Italy. In this photo you can appreciate the rock layers of this beautiful mountain viewing the Gulf of Naples.

 

 

On the path of my excursion, I found (free on the ground) and picked a brown piece of rock that caught my eye because it was different (but not the only one) from all other light gray rocks. Here you can see some photos that show the strange radial texture that cover the top side of the specimen, but also the layered side that is also very interesting and may help identifying it. First of all, is it a fossil or a mineral formation? If it is a fossil, what kind of marine fossil?

 

While writing this topic, I found this map - http://www.isprambiente.gov.it/Media/carg/466_485_SORRENTO_TERMINI/Foglio.html - that shows all the different formations of the mountain. I collected the specimen maybe in CLU or CRQ formation. The map includes the name of all the fossils that can be found in every formation (CLU and CRQ formation's fossils are listed in the first column on the right side), I serched on Google the name of every fossil written in the map, but none of them seems to correspond to my specimen.

 

Please, help me giving a name to this specimen
 

Thank you!

[adriano]

More photos...

 

[supertramp]

maybe you have a layered growth of crystalls with an acicular habit 

 

ciao

 

[adriano]

39 minutes ago, supertramp said:

maybe you have a layered growth of crystalls with an acicular habit 

 

ciao

 

 

I tought the same, but it is also true that the formation is full of fossils. Let's hear someone's else opinion.

[Thecosmilia Trichitoma]

I believe that Italy bans collecting fossils from Italy, so be careful and don't take any away from their original sites.

[abyssunder]

I haven't enough time to study the particularities, but I think, according to the pictures and links provided, the sediments might be from CRQ / CRQ2 (Lower Cretaceous), so it could be a facies described as " alternation of gray crystalline dolomite, often laminated, gray micritic limestone or frequently rolled brown limestone with evident structures and desiccation and / or dissolution, like fenestrae, aligned parallel to the stratification; biomicritic or brown limestones."

The upper surface of the specimen (with concentric and radial patterns) may look like algal growth, but the dimensions are at a different scale, compared to the algae or foraminifera mentioned in the CRQ strata. I can't rule out alga if I look to the Halimeda image below, but I'm inclined to believe that it might be a geological feature, although I'm not convinced.

 

 

[adriano]

21 hours ago, abyssunder said:

I haven't enough time to study the particularities, but I think, according to the pictures and links provided, the sediments might be from CRQ / CRQ2 (Lower Cretaceous), so it could be a facies described as " alternation of gray crystalline dolomite, often laminated, gray micritic limestone or frequently rolled brown limestone with evident structures and desiccation and / or dissolution, like fenestrae, aligned parallel to the stratification; biomicritic or brown limestones."

The upper surface of the specimen (with concentric and radial patterns) may look like algal growth, but the dimensions are at a different scale, compared to the algae or foraminifera mentioned in the CRQ strata. I can't rule out alga if I look to the Halimeda image below, but I'm inclined to believe that it might be a geological feature, although I'm not convinced.

 

 

 

Hey! Thank you for taking your time reading/translating the Italian links I provided - I imagine that it wasn't so easy...

Yes, if it isn't a fossil, I agree that the facies described as "alternation of gray crystalline dolomite, often laminated, gray micritic limestone or frequently rolled brown limestone with evident structures and desiccation and / or dissolution, like fenestrae, aligned parallel to the stratification; biomicritic or brown limestones." is the other best option.

And I also agree that there are many of marine algae/corals that have similar features to my specimen.

 

Today I sent the photos to a friend of mine that teaches Earth Science (in particular tiny fossil algae) in a local University and he said that it can be a limestone concretion (alabaster).

 

I will ask in a minerals forum and see if someone can ID this rock, I'm really curious to know it's name!

[westcoast]

It looks fossily to me. Would like to see a close up view.

[adriano]

On 16/10/2018 at 11:10 PM, westcoast said:

It looks fossily to me. Would like to see a close up view.

 

Here you go...

 

[ynot]

Looks a lot like wethered cave flowstone (calcite).

Does it fizz with vinegar?

[adriano]

1 hour ago, ynot said:

Looks a lot like wethered cave flowstone (calcite).

Does it fizz with vinegar?

 

Yes, it does.

But... Can't fossils be also made of calcite?

 

Anyway thank you for sharing your opinion.

 

Other photos...

 

[ynot]

5 minutes ago, adriano said:

Can't fossils be also made of calcite?

Yes, and there lies the problem.

But this piece looks more in line with a wethered speleothem (cave flowstone).